I am relatively new to fire sprinkler design and using Hydrcad(about 1 month into a new job) and I was wondering at what point do BTS lines stop following the piping and you can specify a new BTS. I have my top of steel references for the entire structure but am having a hard time getting the elevation to lie where i would like it to for the piping ( usually when I specify BTS a few times and rise up into 3D it says that it is over defined and already specified elevation from another point for certain pipes and discards the BTS tag.) I guess my question is how can I follow the system to know what is being elevated by which lines). This is proving detrimental when moving from one room to another with vaulted ceilings and changing elevation. I appreciate the help in advance.
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New to HydraCad and Fire Sprinkler Design
- Thread starter AJ92
- Start date
TravisMack
Mechanical
Does HydraCAD have a user forum? If so, you may want to post in there. That may be the best way to get an answer to your question. I haven't used HCAD in about 15 years, so I don't even recognize the abbreviations you are using.
Travis Mack
MFP Design, LLC
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Travis Mack
MFP Design, LLC
"Follow" us at
HydraCAD is tricky when it comes to using BTS elevations. If you have a building that has different TOS elevations on it you can't define a pipe with a BTS elevation and cross over your differing TOS area. You can only cross that plane with an AFF elevation.
If you had a building that was 10' tall flat steel on one half then jumps up to 25' on the other half if you try to cross it defining a BTS elevation of -24" it will try to jump up from 8' AFF to 23' AFF where it crosses and give you an error.
The best workaround that I ever found was to use AFF as much as possible and never cross your TOS with a BTS elevation.
I used HydraCAD for about 9 years and have been on SprinkCAD for the last 3 years which is a lot more forgiving with BTS elevations.
If you had a building that was 10' tall flat steel on one half then jumps up to 25' on the other half if you try to cross it defining a BTS elevation of -24" it will try to jump up from 8' AFF to 23' AFF where it crosses and give you an error.
The best workaround that I ever found was to use AFF as much as possible and never cross your TOS with a BTS elevation.
I used HydraCAD for about 9 years and have been on SprinkCAD for the last 3 years which is a lot more forgiving with BTS elevations.
First, is this AJ at Aero? If so I can show you on monday lol even if someone helped you fix it, come see me to make sure it was fully explained.
The issue you are having is one I had often when I started. The documentation is not very good. The answer depends on more areas than just the BTS and steel. It could potentially depend on everything in the system you have attached. You can only "SPECIFY" one BTS per branchline. This only works if you are using at least one computer generated riser/riser nipple on your main. If you have your riser to your main "user-defined" then you must have your riser nipples for each branch line set to computer generated.
(Main A) (up) |
-----------O------| (Rn)
|
| (branchline)
Basically hydracad sets the elevation like this: (I'm not sure if this is the "proper" order but it shouldnt matter)
SCENARIO ONE: (pipe flat to floor)
-find lowest specified elevation of all the elevation tags, we will just say your main is 0'-0" A.F.F.
-start at end of the main pipe(main A), continue until there is a riser.
-if riser is user specified(10'-0" Length), increase elevation of the next piece of pipe(main B) to 10'-0" A.F.F.
-continue down the 10'-0" A.F.F. Until we hit a riser nipple.
-if this riser nipple is user specified (2'-0" length) increase the elevation of branchline to 12'-0" A.F.F.
In this scenario, the elevations are driven purely by the riser and riser nipple lengths. The BTS would not be "specified"(you tell it the elevation) but would be "annotative"(hydracad determines the elevation). Once you place the BTS (annotative) tag on it, it will do the math and subtract the elevation (12'-0") from the steel (say 20'-0" A.F.F.) to show a [96 BTS] tag (displays in inches).
Using Riser and Riser nipples to define the elevation is never (99.999% of the time) the correct way to go. Also, defined riser/riser nipple lengths take precedence over Specified BTS or specified AFF. In this scenario if you specified a 6" BTS on the branchline, it would display that error that it is already defined and would remove the 6" tag. This is because the elevation of the pipe is defined already. Trying to Specify BTS essentially tries to override the set elevation and causes a disconnected pipe. (2'0" long vertical pipe from floor would not be connected to a horizontal pipe that has a 4'0" A.F.F.) Also, the BTS & AFF "specify" tags stay with the pipe until there is a riser/rn on the pipe. You could put a 1'-0" BTS at 6" from the endpoint and have a literal unlimited Length of pipe, tees, and turns and they will all remain 1'-0". The ONLY time it will not continue down a line is when it hits a Rn/riser.
Another scene on scenario that is basically the same but more likely to potentially(but rare) a correct way to design is using purely specified A.F.F. Tags. The difference, change all risers and riser nipples to "computer generated" and now set an A.F.F. Tag (10'-0") on Main B from before. Then set the AFF tag (12'-0") on the branchline. Same As above Applies to the specified BTS.
Scenario Two: (works for sloped or flat) *Best method*
(Sloping roof - low side left, high side right)
-pipe drawn the same way, risers/riser nipples computer generated)
-Main A specify A.F.F. (0'-0") (flat)
-Main B specify BTS (36") ONCE ONLY (sloping)
-Branchline specify BTS (12") ONCE ONLY (sloping)
In this case, the computer will set the lengths of the risers/rn just like before. NOTE: you must have top dimensions (BTS) AND one bottom dimension (AFF).
Now, lets say 6'-0" down the branchline the steel has a vertical elevation change (up 12'-0"). The branchline will NOT try and jump to that new elevation provided:
1. the BTS is on the low side only and just once.
2. Your steel is setup correctly. (The T.O.S. must be in the direction as your primary support(girder))
The pipe continues At its current slope. If you need to get to the top of the roof, you need to add a riser nipple after the steel jumps up.
Quick recap, commit to using specify BTS. You can ONLY have one specify BTS/AFF for Any run of pipe that is connected. You may have any number of ANNOTATIVE Bts/aff. If your riser/rn are userspecified the elevation of the next pipe will always move to be connected at the end.
It is extremely important the steel gets setup correctly. If this is AJ from Aero, like i said,
Come see me monday. Otherwise I can get it into that in a response.
The issue you are having is one I had often when I started. The documentation is not very good. The answer depends on more areas than just the BTS and steel. It could potentially depend on everything in the system you have attached. You can only "SPECIFY" one BTS per branchline. This only works if you are using at least one computer generated riser/riser nipple on your main. If you have your riser to your main "user-defined" then you must have your riser nipples for each branch line set to computer generated.
(Main A) (up) |
-----------O------| (Rn)
|
| (branchline)
Basically hydracad sets the elevation like this: (I'm not sure if this is the "proper" order but it shouldnt matter)
SCENARIO ONE: (pipe flat to floor)
-find lowest specified elevation of all the elevation tags, we will just say your main is 0'-0" A.F.F.
-start at end of the main pipe(main A), continue until there is a riser.
-if riser is user specified(10'-0" Length), increase elevation of the next piece of pipe(main B) to 10'-0" A.F.F.
-continue down the 10'-0" A.F.F. Until we hit a riser nipple.
-if this riser nipple is user specified (2'-0" length) increase the elevation of branchline to 12'-0" A.F.F.
In this scenario, the elevations are driven purely by the riser and riser nipple lengths. The BTS would not be "specified"(you tell it the elevation) but would be "annotative"(hydracad determines the elevation). Once you place the BTS (annotative) tag on it, it will do the math and subtract the elevation (12'-0") from the steel (say 20'-0" A.F.F.) to show a [96 BTS] tag (displays in inches).
Using Riser and Riser nipples to define the elevation is never (99.999% of the time) the correct way to go. Also, defined riser/riser nipple lengths take precedence over Specified BTS or specified AFF. In this scenario if you specified a 6" BTS on the branchline, it would display that error that it is already defined and would remove the 6" tag. This is because the elevation of the pipe is defined already. Trying to Specify BTS essentially tries to override the set elevation and causes a disconnected pipe. (2'0" long vertical pipe from floor would not be connected to a horizontal pipe that has a 4'0" A.F.F.) Also, the BTS & AFF "specify" tags stay with the pipe until there is a riser/rn on the pipe. You could put a 1'-0" BTS at 6" from the endpoint and have a literal unlimited Length of pipe, tees, and turns and they will all remain 1'-0". The ONLY time it will not continue down a line is when it hits a Rn/riser.
Another scene on scenario that is basically the same but more likely to potentially(but rare) a correct way to design is using purely specified A.F.F. Tags. The difference, change all risers and riser nipples to "computer generated" and now set an A.F.F. Tag (10'-0") on Main B from before. Then set the AFF tag (12'-0") on the branchline. Same As above Applies to the specified BTS.
Scenario Two: (works for sloped or flat) *Best method*
(Sloping roof - low side left, high side right)
-pipe drawn the same way, risers/riser nipples computer generated)
-Main A specify A.F.F. (0'-0") (flat)
-Main B specify BTS (36") ONCE ONLY (sloping)
-Branchline specify BTS (12") ONCE ONLY (sloping)
In this case, the computer will set the lengths of the risers/rn just like before. NOTE: you must have top dimensions (BTS) AND one bottom dimension (AFF).
Now, lets say 6'-0" down the branchline the steel has a vertical elevation change (up 12'-0"). The branchline will NOT try and jump to that new elevation provided:
1. the BTS is on the low side only and just once.
2. Your steel is setup correctly. (The T.O.S. must be in the direction as your primary support(girder))
The pipe continues At its current slope. If you need to get to the top of the roof, you need to add a riser nipple after the steel jumps up.
Quick recap, commit to using specify BTS. You can ONLY have one specify BTS/AFF for Any run of pipe that is connected. You may have any number of ANNOTATIVE Bts/aff. If your riser/rn are userspecified the elevation of the next pipe will always move to be connected at the end.
It is extremely important the steel gets setup correctly. If this is AJ from Aero, like i said,
Come see me monday. Otherwise I can get it into that in a response.
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